Final answer:
The PEEP/CPAP level is optimum when the PaO2 is maintained within 60 to 100 mm Hg, pressures are below 15 cm H2O, and CaO2 - CvO2 indicates effective oxygenation.
Step-by-step explanation:
The optimum level of PEEP (Positive End-Expiratory Pressure) or CPAP (Continuous Positive Airway Pressure) is determined by a balance of maximizing oxygen delivery to the tissues and minimizing potential side effects. When considering these factors, an optimum PEEP/CPAP level is likely when a physiological balance is achieved where the PaO2 (arterial oxygen pressure) is maintained within the range of 60 to 100 mm Hg, while keeping the pressures low enough to avoid lung injury, typically below 15 cm H2O. An optimal level would also entail achieving an adequate balance between CaO2 (arterial oxygen content) and CvO2 (venous oxygen content), indicating effective oxygen transport and utilization.